In October 2006 an individual of the Common Eider (Somateria mollissima) was examined and 1 female of Trinoton querquedulae was found on one of the remiges. This species of lice was recorded on the studied host for the first time in Poland. Up till now, T. querquedulae has been noted on this duck only in Belgium. Considering the extremely scarce information available, this species of lice is most probably rare in the Common Eider.

Introduction

Chewing lice (Amblycera, Ischnocera) are highly specialized parasites of birds and mammals. They feed mainly on dermal debris, feathers, hair, and skin secretion. Among the largest lice are those of the genus Trinoton, which can be 5-6 mm in length. They have numerous and diverse setae, large and strong legs, which enable them to move freely among the feathers. Apart from feathers, lice can also feed on blood [1]. Chewing lice are parasites of Anseriformes; 5 species were recorded in Poland: T. anserinum (Fabricius, 1805), T. luridum Burmeister, 1938, T. nyrocae Eichler, 1943, T. querquedulae (Linnaeus, 1758), T. spinosum Piaget, 1880 [2-4]. Pathogenicity of these lice is not well studied, but Cohen et al. [5] reported that T. anserinum could transmit filariasis in swans.

In Poland this species was reported from several zoogeographic regions. As the domestic duck is one of its hosts, it is most probably distributed all over the country [2, 3]. Except for the domestic duck, T. querquedulae was found in Poland on the Mallard, Gadwall, Garganey (Anas querqedula L., 1758) and the Teal [3, 14, 15].

This species was recorded on the Eider only once - in Belgium [16]; the present study supports previous finding, moreover it is the first record of T. querquedulae on this host in Poland.
Material and methods

In October 2006, I examined an individual of the Eider (Somateria mollissima), which drowned in the fishing nets in Gdańsk Bay. The feathers were thoroughly examined for lice starting from the head, then neck, back, rump, belly, wings and legs. One specimen of Trinoton querquedulae was found and used to prepare a permanent slide using polyvinyl lactophenol mountant.

Results and discussion

I recorded one female of T. querquedulae (Fig. 1) on the wing of the eider duck – on one of the remiges. Previous study on the other hosts of this louse showed that this species could be found all over the body of the bird, particularly at the base of the bill [17]. T. querquedulae was most often noted on the domestic duck and Mallard, while on the Eider was recorded only once – in Belgium [16].

Other lice species were also recorded on the Eider, i.e. Anaticola mergiserrati (=Anaticola rubromaculatus) (De Geer, 1778), Anatoecus icterodes (Nitzsch, 1818), Anatoecus dentatus (Scopoli, 1763) [16, 18]. Still information on the ectoparasites of the eider ducks is scarce, despite the species could be numerous in some regions of Europe and North America. Up till now no information on the lice of the Eider was available from Poland. This could be due to the fact that this bird species is one of the least numerous sea ducks regularly wintering in Poland, while breeding only exceptionally [19]. Moreover it was also supported by the structure of examined birds – there were only 3 eider ducks among over 150 ducks, which were collected [20, 21, unpublished data].

Usually intensity of invasion of T. querquedulae even in typical hosts is very low, while some increase in number of lice on the domestic ducks is noted in spring [22]. Within 12 mallards examined in Turkey, one specimen of this louse was recorded on one bird only [13], however higher infestation of this host was recorded by Złotorzycka [3] (2.2 individuals). Heavy invasion is noted rarely. However when it occurs then strong feather abrasion is observed, particularly on the back of the bird [22].

The specimen of the louse recorded in this study was measured. Its measurements (total body length 5.61 mm) correspond to data given by other researchers (from about 4.50 mm to 6.10 mm; Table 1).

To conclude – both the results of this study and scarce information on the occurrence of Trinoton querquedulae on the Eider show that it is rare species of this host.